1. Field of the Invention
The present invention relates to a balancing device of a raising-lowering window having a movable shoji opened and closed in the vertical direction.
2. Description of Related Art
In the raising-lowering window for opening and closing the shoji in the vertical direction, a structure having a balancing device for holding a dynamic balancing relation with the shoji weight with respect to the above shoji is arranged so as to simply raise and lower the shoji by slight force and rest the shoji in an arbitrary opening position is known. This balancing device is a device devised so as to apply balancing force balancing with the window shoji through a spiral rod by utilizing the torsional force of a torsion spring. For example, publicly known balancing devices are described in JP-A-3-161683, JP-A-3-180683 and JP-A-4-238984.
These inventions mainly relate to the adjustment of the above torsion spring. Concretely, an adjusting mechanism conventionally proposed is generally divided into a structure for rotating an adjusting shaft arranged in a slide device by a ratchet mechanism in only one direction, and a structure for winding a brake spring of a coil shape around an adjusting shaft and giving braking force to the adjusting shaft by the tight binding force of the brake spring.
However, in the adjusting structure using the above ratchet mechanism, it is very convenient to wind and fasten the torsion spring, but no torsion spring can be unwound. Therefore, this adjusting structure has disadvantages in that the adjustment is limited to one direction, and the torsional force of the torsion spring is released at a stretch, etc. In contrast to this, the structure utilizing the brake spring is more excellent than the structure of the above ratchet mechanism since both the winding and unwinding operations can be performed. However, there is a fearful problem with respect to the braking force using the brake spring. Therefore, problems exist in that the unwinding operation is naturally caused by a slip and slackness is caused with the passage of time so that no sufficient braking function can be maintained for a long period, etc.
Further, the adjusting shaft must be rotated against the brake spring. Therefore, problems exist in that labor taken in the adjustment is large, etc.
In comparison with the above ratchet structure and the above brake spring structure, the balancing device described in the above JP-A-4-238984 is more excellent than the other devices since the braking force is reliably obtained and the unwinding operation is simply performed by skillfully utilizing the rotating direction of the adjusting shaft and a wedge effect. However, problems exist in that the number of parts is large and the structure of a braking portion is complicated, and no stepwise adjustment can be made in the unwinding operation, etc.
Further, as mentioned above, in the case of the balancing device in which no unwinding operation can be stepwise adjusted and the torsional force of the torsion spring is completely released at a stretch, the movable shoji suddenly drops by its own weight when the torsional force of the torsion spring is released in the opening state of the movable shoji and an operator carelessly forgets to support the movable shoji. Therefore, problems exist in that the operator is accidentally injured and the shoji is damaged in certain cases, etc.